Transcript 2-4 Multiplying Rational Numbers Preview Evaluating Algebraic Expressions Warm Up California Standards Lesson Presentation 2-4 Multiplying Rational Numbers Evaluating Algebraic Expressions Warm Up Write each number as an improper.

2-4 Multiplying Rational Numbers
Preview
Evaluating
Algebraic Expressions
Warm Up
California Standards
Lesson Presentation
2-4 Multiplying Rational Numbers
Evaluating Algebraic Expressions
Warm Up
Write each number as an improper fraction.
1. 2 1
3
7
3
2. 1 7
8
15
8
4. 6 2
3
20
3
5. 5 3
8
43
8
3. 3 2 17
5 5
2-4 Multiplying Rational Numbers
Evaluating Algebraic Expressions
California
Standards
NS1.2 Add, subtract, multiply, and divide
rational numbers (integers, fractions, and
terminating decimals) and take positive rational
numbers to whole-number powers.
2-4 Multiplying Rational Numbers
Evaluating Algebraic Expressions
2-4 Multiplying Rational Numbers
Additional Example 1A: Multiplying Fractions
Multiply.
Write the Algebraic
answer in simplest
form.
Evaluating
Expressions
1 6
8 7
1(6)
=
8(7)
Multiply numerators.
Multiply denominators.
3
1(6)
=
8(7)
Look for common factors: 2.
3
=
28
Simplify.
4
2-4 Multiplying Rational Numbers
Additional Example 1B: Multiplying Fractions
Multiply. Write the answer in simplest form.
Evaluating Algebraic Expressions
2 1
– 4
3 2
2 1
2 9
– 4 =–
3 2
3 2
–2(9)
=
3(2)
–1–2(9)3
=
3(2)
Write 4
1
as an improper fraction.
2
Multiply numerators.
Multiply denominators.
Look for common factors: 2, 3.
1 1
= –3
Simplify.
2-4 Multiplying Rational Numbers
Check It Out! Example 1A
Multiply.
Write the
answer in simplest
form.
Evaluating
Algebraic
Expressions
3 5
5 8
3(5)
=
5(8)
Multiply numerators.
Multiply denominators.
1
3(5)
=
5(8)
1
=
3
8
Look for common factors: 5.
Simplify.
2-4 Multiplying Rational Numbers
Check It Out! Example 1B
Multiply.
Write the
answer in simplest
form.
Evaluating
Algebraic
Expressions
7 4
–
8 7
–7(4)
=
8(7)
–1
1
–7(4)
=
8(7)
2
1
=–
2
Multiply numerators.
Multiply denominators.
Look for common factors: 4, 7.
1
Simplify.
2-4 Multiplying Rational Numbers
Evaluating Algebraic Expressions
To multiply a fraction by an integer,
first write the integer as a fraction with
a denominator of 1. Then multiply as
you would with two fractions.
2-4 Multiplying Rational Numbers
Additional Example 2: Application
Joy completes 1 of her painting each day.
20Algebraic Expressions
Evaluating
How much of her painting does she complete
in a 7 day week?
1
1 7
(7) =
Write the integer 7 as a
20
20 1
fraction.
1 • 7 Multiply numerators and
= 20 • 1
denominators.
7
= 20
7
Joy completes
of her painting in a 7-day week.
20
2-4 Multiplying Rational Numbers
Check It Out! Example 2
1
Mark runs
mile each day. What is the total
7
Evaluating
Algebraic Expressions
distance Mark runs in 5 days?
1
1 5
(5) =
7
7 1
1
= I7
•
•
5
1
Write the integer 5 as a
fraction.
Multiply numerators and
denominators.
5
= 7
5
Mark runs
mile in 5 days.
7
2-4 Multiplying Rational Numbers
Evaluating Algebraic Expressions
To multiply decimals, first multiply as
you would with integers. The number
of decimal places in the product is
equal to the sum of the number of
decimal places in the factors.
2-4 Multiplying Rational Numbers
Additional Example 3: Multiplying Decimals
Multiply.
Evaluating
Algebraic Expressions
A. 2(–0.51)
2
 –0.51
–1.02
0 decimal places
2 decimal places
0 + 2 = 2 decimal places.
B. (–0.4)(–3.75)
–3.75
 -0.4
1.500
or 1.5
2 decimal places
1 decimal place
2 + 1 = 3 decimal places
2-4 Multiplying Rational Numbers
Check It Out! Example 3
Multiply.
Evaluating
Algebraic Expressions
A. 3.1(0.28)
3.1

0.28
0.868
1 decimal place
2 decimal places
1 + 2 = 3 decimal places
B. (–0.4)(–2.53)
–0.4
 –2.53
1.012
1 decimal place
2 decimal places
1 + 2 = 3 decimal places
2-4 Multiplying Rational Numbers
Multiply.
Lesson Quiz
Evaluating
Algebraic 2Expressions
1
1. 9
7
1
7
2. 2 – 5
3 8
–5
3. –0.47(2.2)
–1.034
12
1
4
2
4. Evaluate 2 (x) for x = .
2
5
8
5. Edgar runs 9 mile each day. What is the total
distance that Edgar runs in a 7-day week?
2
6 miles
9